function runAsync1(){
    var p=new Promise(function(resolve,reject){
        setTimeout(function(){
            console.log('执行完成1');
            resolve('icessun1');
        },1000);
    });
    return p; // 返回p实例对象
}
function runAsync2(){
    var p=new Promise(function(resolve,reject){
        setTimeout(function(){
            console.log('执行完成2');
            resolve('icessun2');
        },2000);
    });

    return p; // 返回p实例对象
}
function runAsync3(){
    var p=new Promise(function(resolve,reject){
        setTimeout(function(){
            console.log('执行完成3');
            resolve('icessun3');
        },3000);
    });

    return p; // 返回p实例对象
}

// 正确的打开Promise的方法
runAsync1()
    .then(function(data){
        return runAsync2();
    })
    .then(function(data){
        return runAsync3();
    })
